Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
During operation of a wind turbine, each rotor blade is subject to deflection and/or twisting due to the aerodynamic wind loads acting on the blade, which results in reaction loads transmitted through the blade. To control these loads and allow for maximum loading of the rotor blades to capture a maximum amount of wind energy without overloading and potentially damaging the rotor blades and other wind turbine components, the rotor blades may be pitched during operation. Pitching involves adjusting, such as rotating, a rotor blade about a pitch axis. Pitching of the rotor blade adjusts the loading that the rotor blade is subjected to during operation.
In many cases, each rotor blade of a wind turbine is pitched to an individual pitch angle, which may be different from the pitch angles of other rotor blades in the wind turbine. Further, these angles may be constantly or intermittently adjusted during operation. Such pitching operation for the rotor blades beneficially allows for frequent adjustment of the loading experienced by the rotor blades.
However, in emergency conditions, currently known pitching systems and methods may have various drawbacks. For example, in an emergency condition such as a power failure or communication breakdown, communication may be lost between a central controller for the wind turbine, which may control pitching of the rotor blades, and one or more individual rotor blades. Typically, in such an emergency condition, the rotor blades automatically, through various programming, follow a pitching profile to pitch to a feathered position. However, each rotor blade is programmed to follow the same profile, regardless of the individual pitch angle of the rotor blade when the emergency condition occurs. Thus, each rotor blade may follow the pitching profile without consideration of the pitch angle of the other rotor blades. This can lead to imbalances between the rotor blades when an emergency condition occurs, which can cause substantial damage to the rotor blades, the hub, the main shaft and/or various other components of the wind turbine.
Accordingly, an improved system and method for pitching a rotor blade in a wind turbine would be welcomed in the technology. For example, a system and method that reduce the risk of imbalances between rotor blades in the case of an emergency condition would be desired.